Stepping forward to a silicene photonics
The discovery of Graphene, the first thermodynamically-stable 2-Dimensional material, whose exotic electronic properties are based on massless Dirac electrons, has opened a new route in material science. However, a ubiquitous exploitation of graphene is limited by integration issues in modern nanotechnology based on silicon. Indeed, silicon still offers the unique potential to co-integrate electronics and photonics at the nanoscale on a single chip. Reducing silicon to a graphene-like form would bring to a substantial technology throughput opening new and intriguing routes for silicon nanoelectronics and photonics, like engineered and tunable in-gap absorption for photovoltaic application and terahertz detectors and emitters. Recently a collaboration between the CNR-IMM group of Dr. Alessandro Molle and Carlo Grazianetti and the group of Terahertz Spectroscopy at the Department of Physics of Sapienza has provided a new device platform for integrating 2D Dirac electrons in the silicon mainstream technology. At CNR-IMM, say Molle and Grazianetti, we epitaxially grown single layer and few layers 2D silicon on c-oriented (optically transparent) sapphire (c-Al2O3) substrate with a hexagonal (silicene) structure. The electrodynamics properties of these films have been investigated through THz and IR measurements at the TERALAB laboratory of Sapienza, showning an optical response governed by 2D Dirac fermions  which can be modulated by an external bias and then adapted to specific frequency regions. In perspective, the proposed methodology can be further extended to other X-enes (X belongs to group-IIIA, -IVA, and -VA), paving the way to the exploitation of their exotic properties related to the non-trivial topology for applications in the optoelectronics and photonics fields.
 C. Grazianetti et al., Nano Letters DOI: 10.1021/acs.nanolett.8b03169.